**3. Antimicrobial resistance**

have an inherent capacity to resist some antibiotics [3]. However, the rapid surge in the development and spread of AR is the main cause for concern [4]. In recent years, enough evidence highlighting a link between excessive use of antimicrobial agents and antimicrobial resistance from animals as a contributing factor to the overall burden of AR has emerged [5]. The extent of usage is expected to increase markedly over coming years due to intensification of farming practices in most of the developing countries [6]. The main reasons for the use of antibiotics in food-producing animals include prevention of infections, treatment of infections, promotion

Poultry is one of the most widespread food industries worldwide. Chicken is the most commonly farmed species, with over 90 billion tons of chicken meat produced per year [9]. A large diversity of antimicrobials, are used to raise poultry in most countries [10–12]. A large number of such antimicrobials are considered to be essential in human medicine [13, 14]. The indiscriminate use of such essential antimicrobials in animal production is likely to accelerate the development of AR in pathogens, as well as in commensal organisms. This would result in treatment failures, economic losses and could act as source of gene pool for transmission to humans. In addition, there are also human health concerns about the presence of antimicro-

Generally, when an antibiotic is used in any setting, it eliminates the susceptible bacterial strains leaving behind those with traits that can resist the drug. These resistant bacteria then multiply and become the dominating population and as such, are able to transfer (both horizontally and vertically) the genes responsible for their resistance to other bacteria [1, 20]. Resistant bacteria can be transferred from poultry products to humans via consuming or handling meat contaminated with pathogens [21]. Once these pathogens are in the human system, they could colonize the intestines and the resistant genes could be shared or transferred to the endogenous intestinal flora, jeopardizing future treatments of infections caused

Antimicrobials' use in animal production dates as far back as the 1910 when due to shortage of meat products, workers carried out protests and riots across America [25]. Scientists at that time started looking for means of producing more meat at relatively cheaper costs; resulting in the use of antibiotics and other antimicrobial agents [26]. With the global threat of antibiotic resistance and increasing treatment failures, the non-therapeutic use of antibiotics in animal production has been banned in some countries [8, 27–29]. Sweden is known to be the first country to ban the use of antimicrobials for non-therapeutic purposes between 1986 (for growth promotion) and 1988 (for prophylaxis) [27]. This move was followed by Denmark, The Netherlands, United Kingdom and other European Union countries [27]. These countries also moved a step further and banned the use of all essential antibiotics as prophylactic

Several other countries have withdrawn the use of some classes of antibiotics or set up structures that regulate the use of selected antibiotics in animal production [29]. Despite these

of growth and improvement in production in the farm animals [7, 8].

bial residues in meat [15, 16], eggs [17] and other animal products [18, 19].

by such organisms [5, 22–24].

34 Antimicrobial Resistance - A Global Threat

agents in 2011 [30].

**2. Use of antibiotic in animal production**

Bacteria counteract the actions of antibiotics by four well-known mechanisms, namely; enzyme modification, alteration in target binding sites, efflux activity and decreased permeability of bacterial membrane [33]. This expression of resistance towards antibiotics by bacteria could either be intrinsic or acquired. Intrinsic resistance is due to inherent properties within the bacteria chromosome such as mutations in genes and chromosomally inducible enzyme production [34], whereas acquired resistance could be due to the transmission of resistance genes from the environment and/or horizontally transfer from other bacteria [35, 36].
